Radiolabeling brachytherapy sources with Re-188 through chelating microfilms: Stents

Rhenium-188 (Re-188, T-1/2 = 17 h) emits beta particles (E-max = 2.12 MeV) having an ideal range for intravascular brachytherapy and certain cancer br achytherapies. Re-188 was attached to metal wafers and stents via a chelati ng microfilm, and these brachytherapy sources characterized in vitro and in vivo. To prepare the sources, a siloxane film containing reactive amines w as plasma deposited on the metal, a chelating microfilm conjugated to the a mines, and the chelating microfilm used to attach Re-188, Re-188,vas select ively bound to materials coated with the chelating microfilm, Binding corre lated with the amount of radionuclide used. Wafers (1 cm(2)) bound up to 62 .9 MBq (1.7 mCi) of Re-188 with yields generally near 30%. Stents bound up to 26.6 MBq (720 mu Ci). Typically, stents were labeled to bind 4-12 MBq an d deposit 10-30 Gy at 2 mm in the arterial wall. In phantom studies, the lo nger nitinol stents deposited doses of 2.3 Gy/MBq (0.085 Gy/mu Ci), while s horter stainless steel stents deposited 4.62 Gy/MBq (0.171 Gy/mu Ci). After placement in arteries of pigs, only the Re-188-stents were detected by sci ntigraphy at times up to 24 h. Scintigraphy did not detect activity in othe r organs. Blood sampling (0.1-24 h) detected maximum radioactivity (up to 3 88 cpm/mL/100 mu Ci) at 6 h. We conclude that on-demand radiolabeling of st ents and other brachytherapy sources with Re-188 can be performed routinely . (C) 2000 John Wiley & Sons, Inc.